Giardia is a flagellated protozoan parasite that resides in the upper small intestine of several vertebrate hosts, including humans, and is one of the most frequent causes of defined waterborne diarrhea worldwide. Unlike more evolved cells, Giardia lacks of a defined endosomal/lysosomal system, instead it possesses peripheral vacuoles (PVs) with characteristics of endosome and lysosomes, located underneath the plasma membrane. These vacuoles play a central role controlling the endocytosis, degradation, recycling, and secretion of proteins during growth and differentiation of the parasite. The purpose of the present study is to investigate the endocytosis and secretion process of PVs-resident proteins during Giardia growth. We will analyze the role of the molecules involved in protein trafficking from the plasma membrane toward the PVs and characterize novel PVs-resident proteins as well. Because Giardia is an early branching protist, the study of vesicular transport in this parasite will lead to a clearer understanding of the minimal machinery required for protein transport in more evolved cells. Besides, enlighten the endosomal-lysosomal pathway in Giardia may contribute to the design of therapeutic agents against this important human pathogen. [unreadable] [unreadable] [unreadable]